"Unlocking the Phenomenon of Electron Bunching in Quantum Light"
In a groundbreaking experiment, a team of physicists has uncovered remarkable insights into the behavior of electrons when exposed to quantum light. Led by Jonas Heimerl and his colleagues, this study pushes the boundaries of our understanding of light-matter interactions, revealing unexpected and intriguing phenomena.
Traditionally, the photoelectric effect, where electrons are emitted from a material upon exposure to light, has been well-understood when using thermal or coherent light sources. However, the interplay between quantum light and the emission of electrons has remained largely unexplored – until now.
Heimerl and his team generated intense pulses of "squeezed" quantum light and directed them onto a sharp metallic needle tip. This setup allowed them to delve deep into the nonlinear optical regime, where the ratio between the work function of the metal and the photon energy required the involvement of multiple photons to create a single photoelectron.
The results were truly astonishing. Instead of the expected Poissonian distribution of emitted electrons, characteristic of classical light, the team observed a dramatically different pattern. When excited by the quantum light, the number of emitted electrons per pulse became highly unusual – events with either zero electrons or a large number of electrons became significantly more likely than in the coherent light case.
"At a mean of merely 0.3 electrons per pulse, Heimerl and colleagues reproducibly found events with up to 65 electrons per pulse – a result that would occur only once in more than 10^100 repetitions in the Poissonian case," the authors write.
This striking departure from the classical behavior highlights the profound impact that tailoring the quantum-mechanical properties of light can have on electron dynamics. The researchers attribute this effect to the unique characteristics of the "bright squeezed vacuum" they employed, where the vacuum fluctuations are periodically modulated in time, leading to an oscillating uncertainty in the electric field.
Interestingly, the team also observed that intentionally detuning the nonlinear-optical vacuum modulator from perfect alignment caused deviations from the expected "gamma distribution" of electron emission, as the correlations between the even-numbered photon pairs were disrupted.
"In this way, one can in principle tune the electron statistics in an almost arbitrary way – as long as it stays within the constraints of quantum mechanics," the authors note.
This work not only represents a significant advancement in our understanding of light-matter interactions but also opens up new avenues for potential applications. The ability to control the quantum statistics of electron emission could have implications in fields such as particle accelerators, electron microscopy, and beam-based information science.
As the authors conclude, "the work by Heimerl and colleagues represents an enabling and groundbreaking step towards follow-up research addressing this and other questions, because it shows clearly that tailoring the quantum-mechanical properties of light is not only a scientific curiosity but creates extremely strong effects that likely have practical relevance."
Source: https://www.nature.com/articles/s41567-024-02473-5
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